Blower timing system for a gas fireplace

ABSTRACT

Systems and methods for control of a heating appliance blower that provide improved the transfer of heat generated in the heating appliance. By automatically timing when the heating appliance blower turns ON and OFF, the heat generated by the heating appliance can be more effectively transferred away from the heating appliance as desired by a user, for example, to improve heating efficiency of the heating appliance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to airflow control in heating appliances, and more specifically relates to systems and methods for improving heating efficiencies of decorative heating appliances by controlling airflow in the heating appliance.

2. Related Art

The efficiency of a heating appliance is determined based in part on the amount of heat recovered given the amount of energy consumed. Heating appliances consume energy primarily in the generation of heat using, for example, combustion of fuel (e.g., LP, natural gas, or wood/wood pellets) or the conversion of electricity into heat. Another source of power consumption with a heating appliance relates to the way into which the generated heat is delivered for its intended purpose. Operating a blower in conjunction with a heating appliance is a common way to transfer the generated heat to a desired location (e.g., from the heating appliance into a living space). Blowers require power to operate, thus contributing to the overall efficiency of heating appliance.

The heat generated by heating appliances can be transferred in many different ways that also affect the efficiency of the appliance. Some of the generated heat escapes the appliance through the exhaust flue of the heating appliance in the case of a combustion heating appliance. Other heat is transferred into the building structure surrounding the heating appliance, into a living space in which the heating appliance is exposed, or into plenum spaces within the heating appliance. The amount of heat transferred from the heating appliance for useful purposes depends on several variables including, for example, the structure, materials, and location of heating appliance. Some types of heating appliances such as gas furnaces are not intended to provide an aesthetic function and can be designed with maximum heating efficiency as a primary objective. Furnaces typically include a relatively small combustion chamber having outer surfaces exposed to large volumes of airflow and are made of relatively thin metal materials. The combustion chamber structure as a whole retains little heat and is designed to quickly transfer all heat generated by the flame into the airflow engaging the outside surface of the combustion chamber.

Other types of heating appliances, in particular decorative heating appliances such as fireplaces, stove, and fireplace inserts, include relatively large combustion chambers configured to display an actual or simulated decorative flame. The emphasis of many decorative heating appliances is aesthetics rather than efficiency. The structure and materials of decorative heating appliances in addition to their typical mounting within or adjacent to a wall structure of a building, can results in much loss of otherwise useful heat in the heating appliance itself, out of the appliance exhaust system, or into the wall structure. Although significant advances have been made to capture this otherwise lost heat, further improvements are possible.

SUMMARY OF THE INVENTION

The present invention relates to systems and method for controlling air flow and the transfer of heat in decorative heating appliances such as fireplaces, stoves, and fireplace inserts. The disclosed embodiments illustrate example systems and methods relate to control of a blower of the heating appliance, wherein blower control results in improved control and transfer of heat generated in the heating appliance. By automatically timing when the heating appliance blower turns ON and OFF, the heat generated by the heating appliance can be more effectively transferred away from the heating appliance as desired by a user, for example, to improve heating efficiency of the heating appliance.

One aspect of the invention relates to a blower system for use with a heating appliance, wherein the heating appliance including a heat generating unit. The system includes a blower and a blower time control module. The blower timing control module monitors an ON/OFF state of the heat generating unit and controls an ON/OFF state of the blower in response to the monitored ON/OFF state of the heat generating unit. The blower timing control module turns the blower OFF after a first predetermined time period from when an OFF state of the heat generating device is detected, and turns the blower ON after a second predetermined time period from when an ON state of the heat generating unit is detected. The heat generating unit can include a gas valve, and the blower timing system is configured to monitor ON/OFF signals received by the gas valve as part of monitoring an ON/OFF state of the heating appliance.

Another aspect of the invention relates to a method of controlling air flow in a heating appliance, wherein the heating appliance includes a combustion chamber, a blower, and a heat generating device. The method includes turning ON the heat generating device, turning ON the blower, turning OFF the heat generating device, and turning OFF the blower a first predetermined time period after the heat generating device is turned OFF. The method can also include turning ON the blower after a second predetermined time period after the heat generating device is turned ON.

A further aspect of the invention relates to a fireplace that includes a heat generating device, a combustion chamber enclosure defining a combustion chamber wherein heat is generated with the heat generating device, a blower configured to create an air flow in the fireplace, and a blower control module. The blower control module is configured to monitor an ON/OFF state of the heat generating device and automatically control an ON/OFF state of the blower in response to the monitored ON/OFF state of the heat generating device. The blower control module turns OFF the blower after a first predetermined time period from when the heat generating device is turned OFF, and can turn ON the blower after a second predetermined time period from when the heat generating device is turned ON. The control module can also monitor the heat generating device during the first and second predetermined time periods to confirm the ON/OFF state of the heat generating device.

The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description that follow more particularly exemplify certain embodiments of the invention. While certain embodiments will be illustrated and describe embodiments of the invention, the invention is not limited to use in such embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:

FIG. 1 is a front view of a heating appliance including an example blower system according to principles of the present invention;

FIG. 2 is a cross-section view of the heating appliance shown in FIG. 1 taken along cross-section indicators 2-2;

FIG. 3 is a front view another example blower control module according to principles of the present invention;

FIG. 4 is a schematic diagram representing an example blower control module coupled to a valve, power source, and wall switch for a heating appliance;

FIG. 5 is a schematic diagram representing another example blower control module coupled to a valve, power source, and ignition system for a heating appliance;

FIG. 6 is a schematic circuit diagram for the circuit components of the blower control module shown in FIG. 3;

FIG. 7 is a side cross-sectional view of another heating appliance that includes another example blower system according to principles of the present invention, the heating appliance including multiple blowers;

FIG. 8 is a schematic flow diagram illustrating steps of an example method of controlling a heating appliance blower; and

FIG. 9 is a schematic flow diagram illustrating steps of another example method of controlling a heating appliance blower.

While the invention is amenable to various modifications and alternate forms, specifics thereof have been shown by way of example and the drawings, and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention generally relates systems and methods for controlling airflow and heat transfer in a decorative heating appliance. Decorative heating appliances are different from other heat generating appliances in that they include structure that acts as a heat sink (i.e., retains heat during and after shut down of the heat generating features of the heating appliance). Typically, much of this heat is lost without a productive heating purpose. In some cases, users leave a blower of the heating appliance “ON” to capture this heat retained in the structure. Blowers sometimes remain “ON” for extended periods of time well beyond optimum times for efficient transfer of the heat retained in the structure. Efficient heat transfer in this scenario is defined as the ratio between power consumption of the blower and the amount of heat removed from the heating appliance structure for useful purpose.

One aspect of the invention relates to a system that automatically controls the ON/OFF function of a decorative heating appliance blower relative to the ON/OFF state of the heat generating features of the heating appliance. This automated control can result in optimized operation of the blower to maximize efficient heat transfer from the heating appliance. For example, the system delays turning ON the blower a predetermined time after start up of heat generation in the heating appliance. This delay allows the heating appliance structure to become heated before attempting to transfer heat with an air flow from the blower. In another example, the system delays turning OFF the blower a predetermined time after shut down of heat generating in the heating appliance. This type of delay allows the blower to continue transferring heating from the heating appliance structure that may not otherwise be effectively used, while maintaining efficient power consumption by the blower.

Some example decorative heating appliances with which the disclosed systems and methods could be used include gas, electric, or wood burning style fireplaces, stoves and fireplace inserts. Other example heating appliances include universal vent, horizontal/vertical vent, B-vent, and dual direct vented fireplaces, stoves and fireplace inserts, as well as multisided heating appliances having two or three glass panels as side panels.

Referring now to FIGS. 1 and 2, an example fireplace 10 is shown including a blower timing system. The fireplace 10 includes an outer enclosure 12, a combustion chamber enclosure 14, a valve 16, an ignition system 18, a blower 20 and a blower control module 22. Fireplace 10 also includes a plenum 24, a burner 26, a vent assembly 28, and a power source 29.

The combustion chamber enclosure 14 is positioned within the outer enclosure 12 and is sized smaller than the outer enclosure 12 thereby defining the plenum 24. The combustion chamber enclosure 14 includes side panels 30, 32, top and bottom panels 34, 36, front and rear panels 38, 40 and that together define a combustion chamber 42. Portions of the ignition system 18 and burner 26 are positioned within the combustion chamber. The valve 16, ignition system 18, blower 20, blower control module 22 and power source 29 are positioned within the plenum space 24. The ignition system 18 is configured to generate a pilot flame that is used to ignite a main flame of the burner 26. Operation of the ignition system 18 is coordinated with opening and closing of features of the valves 16 to provide gas flow to the ignition system and to the burner for ignition of the pilot flame and the main burner flame. Typically, the valve 16 receives electronic ON/OFF signals for operation of valve features that control fuel flow through the valve 16.

The blower control module 22 monitors receipt of the ON/OFF control signals at the valve 16. When the blower control module 22 identifies receipt of an ON control signal at the valve 16, the blower control module can initiate a sequence of controls related to ON/OFF control of the blower 20. Likewise, when the blower control module 22 identifies an OFF signal at the valve 16, the blower control module can initiate a further sequence of ON/OFF controls for the blower 20.

In other embodiments, one or more sensors may be used to detect the actual presence of a main burner flame at the burner or the presence of a pilot flame of the ignition system to determine the ON/OFF state of the heat generating features of the heating appliance. An example monitoring and control system that describes the use of flame sensors to determine the state of an ignition system or a main burner is described in U.S. patent application Ser. No. 11/238,640, filed on Sep. 28, 2005, and titled GAS FIREPLACE MONITORING AND CONTROL SYSTEM, which application is incorporated herein by reference.

In yet further embodiments, the one or more devices (e.g., thermocouples, thermistors, thermopiles, or thermometers) may be used to detect a temperature within the combustion chamber or other features of the fireplace. When detected temperature exceeds or drops below a predetermined value, the blower ON/Off control sequence(s) is initiated. In one example, a thermistor or thermopile may be positioned inside the combustion chamber, embedded in a panel of the combustion chamber enclosure, within an exhaust duct of the fireplace, or in the plenum defined between the combustion chamber enclosure and the outer enclosure of the fireplace. A blower ON control sequence is initiated when the temperature reaches a specific value such as, for example, about 200° F. to about 400° F. A blower OFF control sequence is initiated when the temperature drops below, for example, about 200° F. to about 300° F. The temperature measure device may be used to measure the ambient temperature of gases in, around, or adjacent to the fireplace, or may be used to measure the physical features of the fireplace.

The temperature measuring device may generate an electronic signal representative of a predefined temperature that is used to activate the blower timing sequence(s). In some embodiments, different electronic signals representative of different temperatures can be generated by the temperature measuring device. The different signals can be used to activate different types of blower sequences or different blower conditions. For example, the blower speed can be increased or decreased in response to signals from the temperature measuring device that indicate incremental increases or decreases in the measured temperature. In another example, a signal indicating a threshold temperature has been met can initiate a blower sequence in which the blower speed increases automatically at predefined time intervals (e.g., every 2 minutes increases blower speed by 10 rpm) over a predefined period (e.g., 30 minutes) or for a certain number of time intervals (e.g., 10 time intervals). A similar scenario is possible for gradually or intermittently decreasing the blower speed, for example, when the temperature signal indicates the temperature has dropped below a threshold temperature.

In another embodiment, the blower operation can be controlled in response to operation of other features of the fireplace besides the ignition assembly and burner of the fireplace. For example, blower operation can be controlled in response to ON/OFF control of backlighting, an ember bed, a simulated flame display, or an electric heat generating unit associated with the fireplace.

In another embodiment, the blower timing sequence(s) may be initiated through ON/OFF activation of the fireplace using a double pole/double throw switch. Such a switch provides starting of the blower timing ON sequence when the fireplace burner ignition sequence is activated by a user turning the switch ON. The switch also provides starting of the blower timing OFF sequence when the fireplace burner ignition sequence is deactivated by the user turning the switch OFF.

Referring now to FIG. 3, an example blower control module 122 is shown including a housing 180, a control knob 182, a test button 184, a label 185, power wires 186, and control wires 188. FIGS. 4 and 5 illustrate example control modules 222 and 322, respectively, which are coupled to a power source 229, 329 and valves 216, 316, respectively. FIG. 4 further illustrates coupling of the valve 216 to a wall switch or control panel 256. FIG. 5 illustrates the valve 316 coupled to an ignition system 318. The control modules 222, 322 monitor signals received from the wall panel 256 or ignition system 318, respectively, to determine the ON/OFF control signals being sent to the valve for ON/OFF control of the valve.

FIG. 6 illustrates a circuit diagram for an example control module such as the blower control module 22, 122, 222, 322 described above. The circuit components illustrated in FIG. 6 include A/D and D/A converters, power regulators, signal noise filters and the like to help monitor and interpret valve ON/OFF signals and provide control signals to the blower.

Referring now to FIG. 7, another example fireplace 100 is shown including an outer enclosure 112, a combustion chamber enclosure 114, a valve 116, ignition system 118, first and second blowers 120, 121, and a blower control module 122. The fireplace 100 also includes first, second and third plenums 123, 124, 125, a burner 126, and first and second vent assemblies 128, 129 having ducts 160, 161. The combustion chamber enclosure includes side panel 130, top and bottom panels 134, 136, front and rear panels 138, 140 that define a combustion chamber 142. An intermediate panel 144 separates the plenum spaces 123, 125. The fireplace 100 illustrates that a blower control module 122 can be used to control multiple blowers and ventilation systems within a fireplace. Fireplace 100 includes a first blower 120 that provides ventilation through the plenum 125 and out of the duct 160. A second blower system including a blower 119 provides ventilation through the plenum 123 and out of the duct 161. Still further blowers and blower assemblies may be provided, all of which may be controlled by the blower control module 122.

In one embodiment using the fireplace 100, the blower control module controls the ON/OFF function of the blowers 119, 120 using different delay time periods. For example, the blower 119 can be turned ON after a delay of 5 minutes from when the main burner is ignited and the blower 120 is turned ON after a delay of 10 minutes from when the main burner is ignited. The blowers 119 may both be turned OFF at the say delay time of 10 minutes from when the main burner is turned OFF.

Example Blower Control System

In one example blower control system, a blower control module monitors a condition of a gas burner of a gas fireplace. In response to the ON/OFF status of the burner, the blower control module controls an air circulation fan or blower at a predefined speed and at specified delay times relative to the burner state. The system operates independent of the ignition controls. The system also uses an A/D sensor input to detect the ON/OFF state of the burner. The A/D sensor detects the presence of a control voltage to a main burner control valve that supplies a flow of gas to the main burner.

The A/D circuit works as a high impedance voltmeter that measures the main burner valve control voltage without adversely affecting the valve control voltage. The range and sensitivity of this voltmeter input is such that it can read the control voltage of both millivolt controls from an AC power source and low voltage dc controls from a battery backup power source. Random burst and spurious noise pulses can be falsely detected as a valve ON operation. The ignition spark noise of intermittent pilot ignition (IPI) systems could be one source of burst noise. The effect of burst noise is minimized by sampling the valve control voltage at consecutive fixed intervals. The sampling interval is of sufficient length to exclude burst noise. The burst noise would typically need to be present at each consecutive sampling window.

Low frequency noise could affect the validity of a detected valve operation. A light bulb on a dimmer circuit could be one source of low frequency noise. This noise is minimized by utilizing the averaging of multiple samples during the sample window. The sampling rate is sufficiently fast to exclude low frequency noise. Low level “white noise” could also affect the detected status of valve operation, especially at the millivolt levels of power. This type of noise is ever present at some amplitude level. To minimize the effects of such white noise, the detection decision level contains hysteresis. The ON detect level is at a predefined minimum above zero volts. This effectively ignores the low noise level at both ON and OFF signals. The use of the multiple samples over multiple intervals and requiring consecutive results is a form of “fuzzy logic” that lends integrity to the burner ON/OFF decision.

A. Power ON Reset (POR) Control Function

At power ON reset, the fan control microcontroller (PIC) initializes by performing self-calibration and setting of internal counters and variables. During a first predetermined time interval (e.g., 6 minutes) the PIC monitors the “manual test button” (TEST) for operation. If TEST is depressed (e.g., test button 184 as shown in FIG. 3), the PIC will check the ON/OFF status of the “burner valve” (valve).

B. TEST Control Function

When TEST is depressed, the fan will come on. This provides the installer an instant opportunity to verify operation and adjust the manual fan speed control for optimum performance. If the burner is OFF, releasing the test button will turn OFF the fan. If the burner is ON, releasing the test button will maintain the fan ON for another predetermined time (e.g., 1 minute). After the expiration of the first predetermined time (e.g. 6 minutes), pressing TEST will turn ON the fan immediately. Releasing TEST will turn OFF the fan immediately. The PIC will not go into the test sequence again and normal operation occurs.

C. VALVE Monitoring Function

The PIC determines the status of the valve at regular intervals (e.g., every minute). This ensures that the valve detection circuit (A/D) is immune to power line noise and spurious emissions of pilot ignition noise within the heating appliance. This immunity of the A/D is further enhanced by the averaging of samples within the sample period. A false ON detect would require multiple signal errors in each of the consecutive sample periods, which are spaced at, for example, 1 minute increments. The VALVE status is determined by measuring the voltage applied to the main burner valve solenoid. This system works with either an intermittent pilot ignition (IPI) or a millivolt standing pilot system. The burner ON detect circuit works independent of the fireplace burner ignition and safety controls. The detected status requires the measured A/D valve value to be above a preset minimum detected voltage to be considered as an ON signal and below that limit to be considered an OFF signal. Thus, the minimum detected voltage level is set above zero in order to provide enhanced noise immunity.

D. NORMAL Operation Function

An internal counter provides a signal at regular intervals (e.g., 1 minute). After each of these intervals (e.g., once each minute), PIC determines the status of the valve. The PIC updates the ON/OFF state of the fan based on the valve and timer values. An ON_TIMER requires that the valve be detected as ON for each interval of a predetermined time period (e.g., 7 consecutive minutes). The fan is then turned ON at a previously selected speed. An OFF_TIMER requires that the valve be detected as an OFF for each interval of a predetermined time period (e.g., 12 consecutive minutes). The fan is then turned OFF. For normal operations the PIC is in a continuous loop checking the state of the valve. On the occasion of power interruptions, brownouts, or ESD, the PIC performs a POR.

Referring now to FIG. 8, the steps of an example method of using a blower timing control system in a heating appliance are described. The method includes a step 300 of turning ON the heat generating device of the heating appliance. A step 302 includes turning ON the blower a first predetermined time period after the heat generating device is turned ON. Step 304 includes turning OFF the heat generating device, and a step 306 includes turning OFF the blower a second predetermine time period after the heat generating device is turned OFF.

Referring to FIG. 9, another example method of using a blower timing control system for a heating appliance is shown. The method includes a step 400 of sending a control signal to the valve to open the valve. Step 402 includes monitoring the valve to determine if an open control signal has been received at the valve. If the signal has not been received, a step 404 includes continued monitoring of the valve. If an open signal has been received, a step 406 includes waiting a first predetermined time period before turning ON the blower in a step 408. In a step 410, a control signal is sent to the valve to close the valve, and a step 412 includes monitoring the valve to determine if a closed control signal has been received at the valve. If the closed control signal has not been received, a step 414 includes continued blower operation. If the closed control signal has been received, a step 416 includes waiting a second predetermined time period. In a step 418, the system continues to monitor the valve to determine if an open control signal has been received at the valve. If an open signal has been received, the system resets to step 410 and 412. If the open control signal is not received during the second predetermined time period, a step 420 includes turning OFF the blower.

The present invention should not be considered limited to the particular examples or materials described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the instant specification. 

1. A blower system for use with a heating appliance, the heating appliance including a heat generating unit, the system comprising: a blower; and a blower timing control module configured to monitor an ON/OFF state of the heat generating unit and control an ON/OFF state of the blower in response to the monitored ON/OFF state of the heat generating unit, wherein the blower timing control module turns the blower OFF after a first predetermined time period from when an OFF state of the heat generating device is detected.
 2. The system of claim 1, wherein the blower timing control module turns the blower ON after a second predetermined time period from when an ON state of the heat generating unit is detected.
 3. The system of claim 1, wherein the heat generating unit includes a gas valve, and the blower timing system is configured to monitor ON/OFF signals received by the gas valve as part of monitoring an ON/OFF state of the heating appliance.
 4. The system of claim 1, wherein the heating appliance is a fireplace, the fireplace comprising an outer enclosure and a combustion chamber enclosure positioned within the outer enclosure, and at least a portion of the heat generating unit is positioned within the combustion chamber enclosure.
 5. The system of claim 2, wherein the blower timing control module delays turning ON the blower at least 2 minutes after the ON state of the heating appliance is detected.
 6. The system of claim 2, wherein the blower timing control module delays turning ON the blower about 1 to about 15 minutes after the ON state of the heating appliance is detected.
 7. The system of claim 1, wherein the blower timing control module delays turning OFF the blower at least 2 minutes after the OFF state of the heating appliance is detected.
 8. The system of claim 1, wherein the blower timing control module delays turning OFF the blower about 1 to about 20 minutes after the OFF state of the heating appliance is detected.
 9. The system of claim 1, wherein the heating appliance further includes at least one sensor configured to determine the state of a flame in the heating appliance and generate a flame signal, and the blower timing control module controls the ON/OFF state of the blower based at least in part on the flame signal.
 10. The system of claim 1, wherein the blower timing control module includes an analog-to-digital converter to convert a voltage reading indicative of a state of the heat generating device to a digital control signal.
 11. The system of claim 1, wherein the blower timing control module monitors the ON/OFF state of the heat generating unit by determining a voltage applied to a main burner valve of the heat generating unit at regular time intervals within the first predetermined time interval.
 12. The system of claim 11, wherein the voltage is above a minimum threshold value that enhances noise immunity of the ON/OFF state.
 13. The system of claim 2, wherein the blower timing control module monitors the ON/OFF state of the heat generating unit by determining a voltage applied to a main burner valve of the heat generating unit at regular time intervals within the first and second predetermined time intervals.
 14. A method of controlling air flow in a heating appliance, the heating appliance including a combustion chamber, a blower, and a heat generating device, the method comprising: turning ON the heat generating device; turning ON the blower; turning OFF the heat generating device; and turning OFF the blower a first predetermined time period after the heat generating device is turned OFF.
 15. The method of claim 14, further comprising turning ON the blower after a second predetermined time period after the heat generating device is turned ON.
 16. The method of claim 14, wherein the first and second predetermined time periods are each in the range of about 2 to about 15 minutes.
 17. The method of claim 14, wherein the first and second predetermined time periods are each at least 2 minutes.
 18. The method of claim 14, further comprising monitoring the ON/OFF state of the heat generating device during the first predetermined time period and aborting the first predetermined time period in the event the heat generating device is turned ON.
 19. The method of claim 18, wherein aborting the first predetermined time period includes resetting to zero a timing device whereon the first predetermined time period is monitored.
 20. The method of claim 15, further comprising monitoring the ON/OFF state of the heat generating device during the second predetermined time period and aborting the second predetermined time period in the event the heat generating device is turned OFF.
 21. The method of claim 20, wherein aborting the second predetermined time period includes resetting to zero a timing device whereon the second predetermined time period is monitored.
 22. The method of claim 14, further comprising varying a blower speed during the first and second predetermined time periods.
 23. A fireplace, comprising: a heat generating device; a combustion chamber enclosure defining a combustion chamber wherein heat is generated with the heat generating device; a blower configured to create an air flow in the fireplace; and a blower control module configured to monitor an ON/OFF state of the heat generating device and automatically control an ON/OFF state of the blower in response to the monitored ON/OFF state of the heat generating device; wherein the blower control module turns OFF the blower after a first predetermined time period from when the heat generating device is turned OFF.
 24. The fireplace of claim 23, wherein the blower control module turns ON the blower after a second predetermined time period from when the heat generating device is turned ON.
 25. The fireplace of claim 23, wherein the control module monitors the heat generating device during the first predetermined time periods.
 26. The fireplace of claim 23, wherein the heat generating device includes a burner, a gas valve, and an ignition system, and the control module monitors at least one of the ignition system function, an open/closed state of the valve, and the presence of a flame at the burner to determine the ON/OFF state of the heat generating device.
 27. The fireplace of claim 23, wherein the heat generating device includes a gas valve, and the control module monitors the presence of a control voltage received by the gas valve to determine the ON/OFF state of the heat generating device. 